The addition of a rolling element thrust bearing at the turning junction between a front McPherson strut mount and the vehicle body provides a steering feel superior to a plain bearing, and several designs have been proposed therefore. An important design objective is to minimize components and provide unitization for ease of handling, since a rolling element bearing is inherently more expensive and more difficult to handle than a plain bearing. But rigorous sealing of the rolling elements still has to be provided, because of the harsh, under body environment.
One approach to unitization and simplification is to provide two basic housing units which snap together, sandwiching a complement of bearing balls between them as a unit. Several examples of such a bearing are disclosed in commonly assigned USPN 4,497,523 to Lederman. One or more of the housings may be molded of rigid plastic, which is strong enough to provide an integral pathway trough for a stamped metal race that in turn supports the balls. An example is shown in FIG. 2 of Lederman '523, where separate soft rubber O rings are used to seal each side of the bearing balls. In an alternate embodiment, FIG. 5, one of the housings is itself molded of softer rubber, which allows a pair of soft rubber sealing lips to be integrally molded with it. Another approach to component minimization and unitization may be seen in commonly assigned USPN 4,541,744 to Lederman. There, both housings are molded of rigid plastic, and snap fit together with a ball separating cage to create a unit. Sealing rings are eliminated by creating a labyrinth seal with flanges and grooves integrally molded to the housings. Of course, a labyrinth seal is not a complete or continuous seal, but rubbing seal friction is eliminated, and a labyrinth seal may be sufficient in certain applications.